From: Nicholas Piggin <npiggin@gmail.com>
To: Richard Henderson <richard.henderson@linaro.org>
Cc: "Nicholas Piggin" <npiggin@gmail.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
qemu-devel@nongnu.org, "Alex Bennée" <alex.bennee@linaro.org>,
"Ivan Warren" <ivan@vmfacility.fr>
Subject: [PATCH] accel/tcg: mttcg remove false-negative halted assertion
Date: Tue, 29 Aug 2023 11:06:58 +1000 [thread overview]
Message-ID: <20230829010658.8252-1-npiggin@gmail.com> (raw)
mttcg asserts that an execution ending with EXCP_HALTED must have
cpu->halted. However between the event or instruction that sets
cpu->halted and requests exit and the assertion here, an
asynchronous event could clear cpu->halted.
This leads to crashes running AIX on ppc/pseries because it uses
H_CEDE/H_PROD hcalls, where H_CEDE sets self->halted = 1 and
H_PROD sets other cpu->halted = 0 and kicks it.
H_PROD could be turned into an interrupt to wake, but several other
places in ppc, sparc, and semihosting follow what looks like a similar
pattern setting halted = 0 directly. So remove this assertion.
Reported-by: Ivan Warren <ivan@vmfacility.fr>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
accel/tcg/tcg-accel-ops-mttcg.c | 11 -----------
1 file changed, 11 deletions(-)
diff --git a/accel/tcg/tcg-accel-ops-mttcg.c b/accel/tcg/tcg-accel-ops-mttcg.c
index b276262007..d0b6f288d9 100644
--- a/accel/tcg/tcg-accel-ops-mttcg.c
+++ b/accel/tcg/tcg-accel-ops-mttcg.c
@@ -98,17 +98,6 @@ static void *mttcg_cpu_thread_fn(void *arg)
case EXCP_DEBUG:
cpu_handle_guest_debug(cpu);
break;
- case EXCP_HALTED:
- /*
- * during start-up the vCPU is reset and the thread is
- * kicked several times. If we don't ensure we go back
- * to sleep in the halted state we won't cleanly
- * start-up when the vCPU is enabled.
- *
- * cpu->halted should ensure we sleep in wait_io_event
- */
- g_assert(cpu->halted);
- break;
case EXCP_ATOMIC:
qemu_mutex_unlock_iothread();
cpu_exec_step_atomic(cpu);
--
2.40.1
next reply other threads:[~2023-08-29 1:07 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-29 1:06 Nicholas Piggin [this message]
2023-09-09 21:28 ` [PATCH] accel/tcg: mttcg remove false-negative halted assertion Richard Henderson
2023-09-21 18:25 ` Michael Tokarev
2023-09-27 10:38 ` Nicholas Piggin
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